[gh-451] upload_replace: Files uploaded through file field have _0 appended

If a file is uploaded through the native file or image field widget with the same file name (use case: updating a pdf) - the new version has _0 appended before the file extension.

The why discussed here: http://drupal.org/node/427212

This is a problem when external applications link to a specific file as I have run into with ehs.unl.edu/sop

I'm proposing making http://drupal.org/project/upload_replace available.